1. Field of the Invention
The present invention relates to power compensation in transmitters and, more particularly, to attenuation and frequency compensation in a radio frequency transmitter in a cellular network.
2. Description of Related Art
In radio frequency transmitters, the power of the output signal may vary due to filtering ripple and uncertainties in internal attenuators. In order to compensate for these power variations, external variable attenuators may be provided. However, these attenuators can only provide a coarse adjustment that is inadequate to compensate for power variations. An analog attenuator with a digital to analog convertor connected to the input of the transmitter may also be provided. Although this allows for a slightly finer adjustment, it adds complexity to the system and increases the expense due to the extra components. A closed loop could also be implemented to provide power adjustment but this would also be expensive and would not provide adequate compensation over a large dynamic range.
Therefore, there remains a need for a method and apparatus for compensating for output power variations in a transmitter without increasing cost or adding additional components.